On 2011-02-15 23:03, Marcelo Tosatti wrote: > On Mon, Feb 14, 2011 at 10:50:42AM +0100, Jan Kiszka wrote: >> Hi, >> >> patch below further reduces the io-thread overhead in tcg mode so that >> specifically emulating smp boxes gets noticeably faster. Its essence: >> poll the file descriptors until select returns 0, keeping the global >> mutex locked. This reduces ping pong with the vcpu threads, most >> noticeably in tcg mode where we run in lock-step. >> >> Split up in two patches, I'm planning to route those changes via the kvm >> queue (as they collide with other patches there). >> >> Jan > > Not sure this makes sense for all cases. There could be scenarios where > a single pass is more efficient (think latency to acquire mutex from > vcpu context in kvm mode, with intensive file IO in progress).
Yeah, likely true. Only TCG has these insane long lock-holding times and requires signal-based mutex handover. I will exclude KVM from this. Jan
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